So imagine a group of enemy archers and spearmen inside of each other. You have the perfect counter on paper: Archers(counter spearmen) & cavs(counter archers).
Now you need a ton of micro because you have to move-command your cav into the bulk of enemies. Then literally click every single cavalry unit to attack a specific archer. You can’t do attack-move because they would also attack the spearmen. Now if the opponent is also kiting his archers away while the spearmen just attack move your cav - you are basically ■■■■■■.
It’s always easier to have range+spearmen then anything else. That’s also why siege is so much better than cav.
The only solution is to give us a “Attack unit by type” command. So you can select your Cav, use this command on an archer and your cav will attack any archer in aggro range until there are none left, then attack whatever.